The name "Easter egg" comes from the Easter tradition of hiding chocolate eggs for children to find. It has a similar meaning in software: an undocumented, hidden feature or message that users may stumble across.

The first software Easter egg is popularly thought to have occurred in 1979. In the early days of software development, programmer identities were jealously guarded. Software studios didn't want their staff to gain celebrity status, their names eclipsing those of the brands they'd created. Warren Robinett, then a programmer for Atari, didn't appreciate this lack of acknowledgement. He couldn't get his name in the manual for the Atari 2600 game Adventure — so he sneaked it into the game itself.

Adventure, despite (or perhaps because of) its simplicity, had a distinctive gameplay that has rarely been duplicated. When in 2005 a high school computer science teacher showed me an educational title I'd never heard of entitled Rocky's Boots, I thought, "This plays like a Warren Robinett game." Sure enough, the credit was his.

Robinett's work has inspired three decades of Easter eggs, and you can still enjoy the original after all these years. Clones of Adventure now exist for MS-DOS and Windows; there's even a Quake 3 mod. Happy hunting, indeed!

What are some of your favorite Easter eggs, whether classic or modern?